JSON to TypeScript Interface Generator
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Trailing Commas: strips [1, 2,] → [1, 2] before parsing.
Allow Comments: strips // and /* */ before parsing.
Switch to Output to see the generated interfaces and copy them directly into your TypeScript project.
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About TypeScript Interfaces
What TypeScript interfaces are
TypeScript interfaces describe the shape of an object — the keys it has, the types of their values, and which fields are optional. They are the foundation of type-safe JavaScript development.
Type safety from day one
Defining interfaces for your API responses means TypeScript catches mismatches between what your backend sends and what your frontend expects at compile time, not at runtime.
Essential for large codebases
As a codebase grows, untyped API payloads become a major source of bugs. Generating interfaces from real payloads is the fastest way to retrofit types onto existing code.
Why this tool helps
Writing interfaces by hand from deeply nested JSON is slow and error-prone. Pasting a real API response here gives you a working type definition in seconds.
Benefits
Why generate TypeScript interfaces
Hand-writing interfaces for large API payloads is tedious and error-prone. Generating them from real data is faster and more accurate.
Catch API drift early
When a backend changes a field type or renames a key, TypeScript interfaces catch the mismatch at compile time before it reaches production.
Better IDE autocomplete
Typed API responses give you autocomplete on every field when you write code that consumes them — no more guessing key names from documentation.
Documents the API shape
Interfaces serve as living documentation for the shape of your API. Generated interfaces from real payloads stay accurate longer than hand-written docs.
Built for accurate TypeScript interfaces
Infers types from real values, generates sub-interfaces for nested objects, and produces clean output you can paste directly into your codebase.
Nested objects become sub-interfaces
Each nested object generates its own named interface. The root interface references sub-interfaces by name rather than using inline anonymous types.
Null fields become optional
Fields whose value is null in the sample JSON are marked as optional (?) in the generated interface, reflecting the real-world uncertainty of the field.
Array element type inference
Array fields infer their element type from the first item. Object arrays generate a named item interface; primitive arrays use the correct primitive type.
Safe key quoting
Interface keys that are not valid identifiers (containing hyphens, spaces, etc.) are automatically wrapped in quotes: `"my-key": string`.
In-browser, no upload
Type generation runs entirely in the browser. API responses containing sensitive data never leave your machine.
Questions about TypeScript interface generation
Common questions about the interfaces generated and how to use them.
Yes. The output uses standard TypeScript interface syntax. Paste it into any .ts or .d.ts file and it will compile without modification.
The element type is inferred from the first item in the array. If the array is empty, the element type is unknown[]. For object arrays, a named sub-interface is generated for the element type.
Fields whose value is null in the sample JSON are typed as null and marked optional with ?. You can widen the type manually if the field can also hold other values.
No. Interface generation runs entirely in your browser. API responses containing sensitive data or internal field names never leave your machine.